Many traditional shaping techniques exist for forming loose masses of particulate, fibers, whiskers, etc., into a desired shape followed by some set of processing conditions which typically involve high temperature exposures. For example, many traditional ceramic processing techniques such as slip casting, dry pressing, isostatic pressing, hot pressing, extrusion, etc., each involves the consolidation of an initial loose mass or unbonded array of constituents into a shaped member having at least some structural integrity. Moreover, in each of these techniques some means for initially holding the loose mass together until the loose mass can itself consolidate into a preferred shape is necessary. Common to many of the traditional approaches is the use of a binder system which imparts at least some initial "green" strength to the body to permit the body to hold its predetermined shape.
Further, common to each of the aforementioned traditional techniques is the application of thermal energy. A primary purpose of the application of thermal energy is to permit individual constituents of the green body to begin to, for example, sinter together to form a more rigid body. Typically, when such sintering occurs, a part will change in size and/or shape due to porosity in the green body being consolidated. It is during such sintering operations that cracking, bending, and/or uncontrolled shrinking may occur. The art is replete with many techniques for controlling undesirable aspects associated with traditional sintering processes.
The art also includes processing techniques for the formation of composite bodies. For example, rather than starting with any of the constituents discussed above and causing such constituents to consolidate into a dense, shaped body, the art teaches that porosity in a first material can be filled with a second material to form a desirable composite body. For example, the porosity in a first formed body could be filled with an inorganic material such as a ceramic or a glass, a polymer, a metal or alloy, an intermetallic and the like. The impetus for forming a composite body is to achieve a synergistic interaction between the constituents of the composite. Specifically, a single material by itself may not be able to withstand certain corrosive and/or erosive environments and/or certain high temperature environments, etc. However, by combining two or more materials together, desirable attributes of both materials may be utilized to overcome the shortcomings of a single material.
A key element for reliably and economically producing desirable composite materials involves the ability to produce economically and reliably a shaped first material into which a second material can be introduced. Many techniques exist for shaping a porous first material into an acceptable body for introduction of a second material or matrix therein; however, the search continues for better techniques to form porous first materials. This invention attempts to satisfy the need for achieving a reliably and economically produced first material which reliably and economically accepts a second material to result in a desirable composite body.